Telephone-exchange system



Sept. 29, 1925.

E. A. GRAY TELEPHONE EXCHANGE SYSTEI IN VEN TOR Filed Jun@ 25. 1923 yma/1, A TTORNEY E. A. GRAYv Reyno! sept, 29, 1925.

INVENTR Ej. 6fm;

BY I jATTR/vev -ooo oog/ J Ddr/ankh Tadel Patented Sept. 29, 1925.

UNITED STATES PATENT OFFICE.

ERNEST GRAY, 0F ROSLYN, NEW YORK, ASSIGNOR T0 AMERICAN TELEPHONE ANDTELEGRAPH COMPANY, .A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application led J'une 25, 1923.

To all a0/10m, t may concern:

Be it known that I, ERNEST A. GRAY, residing at Roslyn, in the county ofNassau and State of New York, have invented certain Improvements inTelephone-Exchange Systems, of which the following is a speci- .licationThis invention relates to telephone'signaling systems and particularlyto means for and a method of operating long distance toll telephonelines in order to increase the efficiency of such systems.

In operating long distance toll telephone lines it has been heretoforecustomary for the operator at the office where the call originates tosignal the operator at the distant oliice and order that operator toestablish the connection to the called telephone. In such system it isnecessary for the calling opera tor to hold the long distance toll lineuntil the called telephone is answered and a report is obtained. It isobvious that such a system is never very efficient inasmuch as the tollline is not available for revenue producing use during the time in whichthe calling operator is holding the toll line while await- .ing a reportfrom the called telephone. In the operation of toll telephone systemsthe total time per call consists in what may be termed the operatingtime plus the length of conversation. The operating time consists in thetime necessary for completing all of the steps to establish a.connection between the calling and the called subscriber and to put themin communication with each other. If we assume that the length ofconversation is approximately fixed, it will be seen that by reducingthe. operating time the total time per call may be accordingly reduced.By thus effecting a reduction in the total time per call, a largernumber of calls per hour may be transmitted over a given circuit wherebythe eiiiciency of the system may be increased. y

It is the object of this invention to provide means for and a method ofoperating a signaling circuit and particularly a long distance tolltelephone system whereby greater volume of revenue producing traffic maybe handled over a toll line than is now possiblev by the presentring-down method of operation.

p tor` will be referred to.

Serial N o. 647,676.

toll lines are not held by the calling or out- Award operators until thecalled telephone is answered and a report is obtained as in thering-down method of operation, but such lines are used to pass thedetails of other calls up to the time when any two parties are ready totalk. It will be clearly seen from the following description that duringany interval in which the toll lines are not being used by the partiesfor the purpose of conversation between themselves the details of aplurality of calls may be transmitted bythe calling or outward dispatchoperator to the called or inward dispatch operator, and similarlyreports upon such calls may be transmitted by the said inward operatorto the said outward operator whereby the proper terminal circuitarrangements for a plurality of calls may be established in advance ofthe time when a toll line is available to complete the connection. Assoon as any toll line becomes available the proper terminal connectionsfor the next call will have been established thereby minimizing the timeduring which any toll line is not employed for revenue producingconversation.

The dispatch method of operation normally involves the use of threeoperators at each end of a group of toll line circuits, one of whom isknown as the dispatch operator and the others as the report operators.For the purpose of describing this system only the dispatch operator andone report opera- The function of a report operator is to deal withsubscribers and with operators at local ollices through which thesubscribers may be reached, receiving the calls from the subscribersthrough the said oii'ices, giving reports on such calls and supervisingthe starting of conversation and timing of messages. The dispatchoperator controls the toll line circuits between the toll offices,passing and re ceiving calls, reports and orders over the said circuitsand connecting the subscribers line with the toll line circuit when boththe calling and the called parties are at their telephones ready totalk.

This invention will be clearly understood from the following descriptionwhen read in connection with the attached drawing oi which Figures l and2 represent one terminal circuit when the figures are correctlyassociated by placing the top of the sheet containing Fig. l adjacent tothe bottom of the sheet containing Fig. 2. Fig. 3 shows the switchboardarrangements for carrying out the system described herein, and Fig. 3shows a detail thereof. Figs. 4, 5 and 6 represent schematically thecircuit connectionsunder various conditions iii-which the dispatchsystem may be involved which may be designated the terminal dispatchsystem, the built-up dispatch system and the tandem dispatch system,respectively. For the sake of brevity the description of this inventionwill be limited to the terminal dispatch system as shown in Fig, l.

In the terminal circuit represented b-y Figs. l and 2, when associatedin the manner directed, the apparatus lying between the lines X K and YY is located at the report operators position of the switchboard and theapparatus lying between the lines Y YA andV Z Z is located at thedispatch table. The relative arrangement of the report positions and thedispatch table is shown in Fig. 3 wherein the dispatch table is placedbetween and in back of two positions of the switchboard' which therebybecome the report positions for the said dispatch table. AtA each reportposition a plurality of toll lines suchas L1 and L2 to other tolloliices terminate in the line jacks J1 and J2 respectively, which havein multiple therewith at other positions of the switchboard'the jacksJ1. and J2. Also each. report position has a plurality of pluggingupcords, the plugs of which are represented by P1 and P2. The cordcircuits of which the cords connected with P1 and P2 form a part extendto the dispatch table, each terminating there in a cord and plug such asP7. For the sake of simplicity only one complete cord circuit has beenshown namely that which terminates at the dispatch table in the plug P7.This cord circuit embraces a ringing key K7, a. splitting key K2 and a'talking key K5 which are located at the dispatch table. Bridgedacrossthe conductors of this cord circuit between the ringing andv thesplitting keys is the relay Rl responsive to ringing current transmittedthrough the cord circuit. This relay controls the operation ot thesignal lamp S7. The pilot lamp S2, which operates whenever Sl does, iscontrolled by the relay R2 which in turn is controlled by relays R3 andR4. The supervisory lamp signal S3 is controlled by the relay R5.Associated with the talking key K3 is the dispatch operators telephoneset which need not be described in detail since any well known type ofset may be used with this circuit.

At the report operators position there also terminate the lines L3 andL2 which represent switching trunks to local central oiices where thesubscribers7 lines terminate. These switching` trunks serve to connectthe subscribers with the long distance toll offices. These lines L5 andyL4 may also represent long distance ring-down trunks to other tolloffices not operated uponthe dispatch system.vv These linesterminate inthe jacks. J 3 and J 4, respectively, at the reportl positions whichhave in multiple therewith the jacks J5 and J 5 respectively at otherswitchboard positions.y Extending from each report position to thedispatch table is a plurality of trunks, which terminate at eachl placein a plurality of jacks having signal lamps associated therewith.designated assignment trunks are' represented by L5 and LG which'terminate at the report position in the jacks J5 and JG, respectively,having the jacks J5 and J 5 multipled at the adjacent report'position..The

signal lamps S5 and S5 are associated with the jacksJ 5 and J5 at therespective report positions and similarly are the lamp signals S6 andSG. Also at each report positionis a plurality of toll cord circuits'vsimilar to` that terminating in plugs P3 and P5. Each of these cordcircuits has the usual ringing.

splitting and talking. keys designated K5, K5 and K5, respectively, andaplurality o f relays suoli as Rf6 to R5, inclusive'. The object! of thetoll cord circuits'just' described is to establish a connection between'the switching t-runkssuch as L3 and L4 and the assignment trunks suchVas L5 and L, the

purpose and the manner of doing. which wvill be clear from subsequentdescription The assignment trunks` represented, for' example, byL5'terminate at the dispatch table in jacks such as J7 which have' otherjacks such as J7 in multiple therewith at` other dispatch tables. The jack- J7, whichl is located at what may be termed the home table, hasassociated therewith two lamp' signals designated S7 and S8 which arecon.-

trolled in part by the operation ot the relays R12, R and Rip Themultiple-jack J7 has also a lainpsignal S5 associated therewith. Thejack J 7, or its multiple J7, is

adapted to have inserted 'therein a plug suchl as P7 of the cord circuitthat extends from the dispatch table of the report position at theswitchboard terminating therein in a plug P1 which is intended to beinserted in a jack such asv J1 of the line L1 thereby establishing aconnection over thel dispatch toll line L1 with the distant tollIoiltice.

Tt is to be understood that at the distant' toll oi'hce the circuitarrangement and the These trunks which are position of the operatorswill be exactly identical with that described above.

Having in mind the foregoing description of the circuit arrangement of adispatch toll system, the method of operating the terminal dispatchsystem will now be described.

Temi/nal dispatch S11/stem.

A schematic circuit of the terminal dispatch system is shown in Fig. 4.In this system, the calling subscribers line designated No. l isconnected at the local central office No. l with a. switching trunk No.l extending from the said central otlice to the dis'- patch toll oiiiceA (which thereby becomes the outward oiiice) terminating therein in ajack at a report position of the switchboard. This switching trunk isconnected by means ot a. cord circuit with an assignment trunk extendingto the dispatch position, which trunk is there connected by means of acord circuit with the long distance toll line eX- tending to thedispatch toll oiiice B (which becomes the inward office). At the latterolice the toll line is similarly connected with an assignment; trunkextending to the report position, which trunk is there connected with aswitching trimk No. 2 extending to the local central otiice No. 2, atwhich terminates the called subscribers line No. 2. The circuit justdescribed represents the complete talking connection between the callingand the called subscribers. It is designated a terminal dispatch systembecause the calling and called subscribers lie within the Zones forwhich the long distance telephone service is provided by the tolloiiices A and B, that is to say, the routing of the call requires noother toll oiiices.

The method of operating such a system is as follows: l/Vhen a callingsubscriber located in the Zone of oiiice A desires to talk with anothersubscriber in the Zone of oiice B, the said calling subscriber isconnectedby his operator at the local central oice No. l with arecording operator at the toll oiiice A. The recording operator notesupon a ticket the name, address or telephone number of the-.called partyand also the name and telephone number of the calling party. 4Thisticket is transmitted to the report operator, at whose position thedispatch toll lines between A and B terminate. The report operator at Aplaces the ticket in the report clip upon the dispatch table, as shownin F ig. 3. The dispatch operator at A takes the ticket and passes thedetails of the call to the dispatch operator at B, who records thedetails on a serially numbered ticket,'which serial number is given toand noted by the dispatch operator at A upon her ticket. The dispatchoperator at B at, the same time assigns the particular call to anassignment trunk extending between the dispatch table and a reportposition at the switchboard.

Both .dispatch operators note the trunkassignment upon the backs oftheir respective tickets and place the tickets in an unnum* beredclip atthe rear of the dispatch table and to the right-hand side thereof. Theuse of assignment trunks having the same number simplifies theprocedure.

The report operator lat A takes the ticket from its clip and orders upthe subscribers line. The manner of doing this will be clearlyunderstood from the circuit diagram shown in Figs. l and 2. 'llhe reportoperator at A inserts the plug P3 in a jack J 5 of the switching trunkL5 which extends to the local office. This may be either a ring-down oran order wire trunk. Regardless of the character of the trunk, thereport operator tells the local operator to connect the callingsubscribers line with the-said trunk. The subscriber is not called atthis time `but the line is held under the control of the reportoperator. The report operator then inserts the other plug P5 of thiscord circuit in the jack J5 of the assignment trunk L5 that eX- tends tothe dispatch table and terminates there in a jack J 7. Vhen the plug P5is inserted in the jack J5 current will flow from the battery 1associated with the relay R9 through the sleeve contacts of the plug P5and the jack J5 and through the winding of the relay R12 to ground,thereby operating relays R5 and R12. The signal lamp S10, associatedwith the cord P5 would tend to light upon the operation of relay R9 butthe current How therethrough from the battery 2 would be shunted throughconductor 7 and accordingly theV lamp remains dim. The operation ofrelay R12 associated with the assignment trunk L5 removes a ground fromits left-hand Contact and connects the grounded battery 3 with itsright-hand contact. Consequently, current will How from battery 3through the right-hand contacts of relays R12 and R13 and through thesignal lamps ST and S9 to ground thereby lighting the said signal lamps.It should be pointed out that certain assignment trunks are used foroutgoing calls, that is, calls going out from oliice A to another officeand other assignment trunks are used only for calls incoming to oiice Afrom another oiiice. For the purpose of describing this invention trunkL5 :has been assumed to be an outgoing assignment trunk and L6 anincoming assignment trunk. In order to enable the dispatch operator toreadily distinguish the assignment trunks assigned to outgoing orincoming calls, inasmuch as the operating practice varies slightly, thelamp caps upon ythe O. K. signal lamps, such as S7 and S9 associatedwith the trunk L5, are colored green while the caps for the similarlamps S12 and S11 associated with the incoming assignment trunk L6 arecolored white. At the dispatch toll office B, the assignment trunk theredesignated .also as lL5 '.Willihave White O. K. signal lamps:becausetrunk VL5 at Athat ottice :is an .incomingztrunk And in similarmanner the assignment trunk also designated L5 atoffice iB Will 'havegreen O. K. lamp signals because -it is an outgoing'trunk at office B.It Willzaccordingly be seen that when the dispatch Koperator .at Bassigned, for example, trunk fLG to the call that had been transmitted:to ther and both @dispatch operators had noted this :trunk number onthebacksot `their respective tickets,that this number means an incomingtrunk at oiice B and an outgoing trunk at oiiice A,.although both'trunkshave the samedesignating number.

`=When the report xoperatorat A has secured the fcalling :partys lineand `hasconnected it with the .proper assignment trunk, she places Qtheticket in that assignment clip at the .rear ofthe dispatch table Whichbears the same number .as the lassignment trunk and-simultaneously shetakes Ifrom that clip a tag Abearing the :number of vthe trunk andplaces this tag in a lclip iin front of thecords connected with 'theplugs P5 and P5. This tag serves as -a means vfor readily .identifyingthe callassociated Withlthis cord-circuit.

At. the toll oliice B the procedurelis-somewhat similar. The report.operator at B` takes the ticket "from the unnumbered clip and inserts a:plug similar to P5 into a `jack similar to J 5 of a line similar to L5and calls the loperator ,at the central office Where :the called partysAline terminates. If the report operator-at vB reaches ithe called partyand he is ready sheadvises him that he will be called again in a fewminutes and When he hangs up lhis 4receiver she inserts a plug of -thelcord circuit .corresponding to TP5 in a ljack corresponding to JG ofthe assignment trunk :bearing the number L5, Which operates the 1C). iK,Vsignal Yat =the dispatch table iB. It shouldlbe remembered, however,that since ithis is an incoming call at oliice B :the assignment 'trunkthere has a White lampcapover the O. `K. signal lamp. 'If the reportoperator at B has secured the called party yin the .manner described shelplaces the `ticket in the ticket-clip in front ofthe cords olil thecord circuit connecting the switching trunk :to `the assignment trunk.H, on the other hand,thereportoperator is unable 'to reach the calledparty, she Will note upon the ticket such report as she has been able.to obtain and place .the vticket in the `reportclip attlieyright-handside of the dispatch table. The ymethod of .handling suchreports yWill bedescribed later.

As soon as thev dispatch operator at B receives lthe xwhitelamp signalindicating that the called subscriber y'has been reached, the dispatchoperator at B, using any .non-:busy toll line such as lL1 or L2, passesAto fthe A dispatch operator an vorder such as 0. K.

L5 indicatinganot only that she `has secured the calledipartys `line butalso .that such panty zisavailable forr'eceiving theicall. The dispatchoperator at A upon receiving the green :lampsignal S, .Will accordinglyassign a .toll 'line ',to :this .caill assuming,` oi course,

that a toll line is available. The dispatch operator at A will insertthe plug P, in the jack J7, thereby connecting lthe toll line L1Withftheassignment trunk- She then operates "her ringing key :K1 in aright-hand direction :so as fto ringfthe calling subscribers and at thesame instant operates the splitting :key K2 of fthe cord circuit.connected with the plug l), so as ,to keep :the .line L1 effectivelydisconnected from the assignment trunk in Yorder .that this toll linemay continueto be used for `further .interohice business. lipon "theinsertion of 'the plug P.

in theujackfJ7 current will loW from battery athroughrthe sleevecontacts of the plug vP7 and jack J, :over vconductor 5 and through theWindingo` relay R15 :to ground, thereby operating the said relay. By theopening of .its right-'hand .contact vthe O. fK. signal lamp attheitlispatch table is extinguished. By theclosingof its inner.left-hand Contact current flows lfrom battery 6 through the guardi.lamps S5 and S5 associated with jacks J5 and.J5. The operation of thelamp S5 .informs the report .operator :that a toll line has beenassigned to thiscall.

Vhen vthe dispatch operator at A inserts the plug lP7 in the -j ack J7,she operates the ringing and splitting :keys K1 vand 'K2 ofthecordcircuit.connecting ,thetoll line with thelassignmenttrunk. Theoperation of the split-ting key ytends to .keep the toll lineeffectively disconnected from the 4terminal circuit and thereforerenders it practicable to use this toll line for .transmitting new callsbetween 'the'.dispatch yoperators at A and B. illhe operation of theringing keys K1 applies 4ringing current from the source 8 overithe-tiplandring conductors ofthe cord connected Withithe plug P7, thence overthe assignment trunk L5, thence Athrough the cord circuitat the reportoperators position and over the switching trunk L3 and the subscribersline to 'the calling subscribers station thereby ringing ythe distantsubscrib er?sstation. 'This ringing current operates relay `R5associated with the cord circuit at fthe 4reportoperators position whichre moves the shunt path around the signal lamp S,n :causing 4this lampto light.

The iepoitoperatorat A, upon seeing the tollcordsignalS10 lighted, notesfrom the numbercheck in the spiral clip associated with the cord pairthe assignment trunk number. She then removes lthe ticket Jfrom thenumbered spiral corresponding to the assignment trunkfnumberzon :top ofthe dispatch tableand returnsthe number check to its numbered spiral.As-soon as the calling CIJ subscriber answers by removing his receiverfrom its hook, the subscribers supervisory lamp signal S11 will operateas the result of the operation oit' the relay R10. The report operatorwill advise the calling party that she is ready with the called party,and when the calling party orders the connection established, the reportoperator operates the splitting key K5 of her cord circuit andsimultaneously rings over the assignment trunk by operating the ringingkey K1 in a left-hand direction. The ringing current applied to theassignment trunk L5 from the source 9 Will be transmitted to the cordcircuit at the dispatch table, but Will not pass on to the toll linebecause the splitting key K2 at the dispatch table is operated.

This ringing current will, however, energize the relay R1 associatedWith this cord circuit which will remove the shunt path around the lampS1 thereby permitting the said lamp to light and will apprise thedispatch operator at A that the subscriber has anlslwered and is readyto go ahead With the ca While these operations have been going on at thedispatch oiiice A, similar operations have been carried o-n at B. Assoon as the dispatch operator at B received from the dispatch operator Aan assignment of a toll line, she inserted the plug ot' her .cordcircuit corresponding to P, in a jack corresponding to J1 and operatedthe ringing and splitting keys of her cord circuit in a manner similarto that described above. The application of ringing current not onlyoperated the bell at the called station but also operates a toll cordsupervisory signal lamp corresponding to S10 at the report operatorsposition at the B otiice. Upon seeing this lamp lighted, the B reportoperator removes the ticket from the spiral clip associated With thecord pair at her position, and as soon as the called subscriber answers,as indicated by the subscribers supervisory signal similar to S11, sheadvises the'party that she is ready with the calling subscriber. As soonas she is ordered by the called party to go ahead, she operates hersplitting key and then rings over the assignment trunk by Y operatingher ringing key corresponding to K1. As the result of this ringing oeration, the signal lamp corresponding to Si at the dispatch table atolice B will bev operated.

The dispatch operator at B, upon noticing the operation of the signallamp S1, says to the dispatch operator -at A that she is ready on theline L1.

The dispatch operator A also having received the signal from her reportoperator by the operation oit the lamp S1, tells the dispatch operator Bto go ahead on the line L1. The passing of the ready and the go 1 ahead7orders may be done by either dispatch operator. The iirstk dispatchoperator Who notes the toll cord supervisory signal such as S1 lightedpasses the ready order, which is ollovved by the other dispatchoperators go ahead as soon as she notes her corresponding` signal.

The dispatch operator A again operates her ringing key K1, whichtransmits ringin@r current over the assignment trunk L5 an operates therelay B0 associated With the cord circuit at the report operatorsposition whereby the supervisory lamp S10 is lighted. This ringingcurrent will not pass over the switching trunk to the subscriber vvho isthen at his telephone, because it Will be remembered that the splittingkey K,1 at the report operators position is operated so as to split thecord circuit. The dispatch operator at A also restores her splitting keyK2 to its normal position, so that the toll lineV L1 is effectivelyconnected over the assignment. trunk L5 to the report operatorsposition.

'-As soon as the report operator A sees the toll cord supervisory lampS10 lighted, she operates her splitting key K5 in the opposite directionso as to connect her telephone set with that side of the cord circuitconnected With the assignment trunk L5 thereby connecting her with thecalled party.

lVhile these operations have been going on at the A dispatch oiiice,similar operations have been carried on atthe B oiiice. There thedispatch operator operated her ringing key corresponding to K1 as soonas she received the go ahead signal from the dispatch operator at Aandsimuitaneously. restored her splitting key corresponding to K2 to itsnormal position. The ringing currentV operated a lamp similar to S10 atthe report operators position at B, and upon the receipt` of this signalthe report operator re` stored her splitting key to normal andsupervised the connection suiiiciently to see that such connection hadbeen properly established. These operations at oiiices A and Barecarried out practically simultaneously,`

so` that the report-operator B Will have restored her splitting key toits normal position by the time that the report operator A has operatedher splitting key in such direction as to enable her to talk vvith thecalledparty.

As soon as the report operator at A meets the called party, Whichtherefore insures that the talking connection is properly established,she restores her splitting key to `its former position, therebyconnecting her telephone set with that part ot the cord circuitconnectedivith the calling-party and tells the calling partyr to goahead. The report operator then restores her splitting key to its normalposition thereby connecting the calling and called parties.

As soon as the calling and the called parties terminate theirconversation and hang up their receivers, the subscribers dis- :thewinding of relay R12- connect signals such as S11 and S34 are oper atedin the cord circuit at the report position andl also in the cord circuitat the4 dispatch position at both ends of the line. The Aoperation ofthe disconnect signal at the dispatch tables gives to the respective'dispatch operators the information that the toll line is clear andavailable for reassignment,so that these dispatch operators do not haveto wa-it for thek receipt of such information from their' correspondingreport positions. lf a'- report operator suchas' at A disconnects her'cord' circuit from the assignment trunk by withdrawing the'plug P5 fromthe jfac-k J5, the dispatch operator at A would be so advisedv by theflashing of the signal lamp SW The withdrawal of the plug P from the ackJ5 disconnects battery from l A Thel releasel of relay R12 closes itslett-hand and opens its right-handvr contacts. A circuit is thereforeestablished which includes the grounded interrupter 10, left-handcoi'it'act of relay R12, outer left-hand contact of relayRls, ringcontact of `jack J', and plug P7, ring conductor of cord circuit atdispatch table, contact of key K1, winding of relay R15 and groundedbattery l2. Relay R5 would be intermittently operated and theV lampsignal Swould flash, thus attracting' the attention of theV A dispatchroperator. This insures the. prompt releasing of the toll. lines forother calls. p y y Vhen the report operator at B is unable to reach thecalled party, that is to say, the

called telephone is not answered, or, if answ'ered, the calledparty isnot there, the procedure is different from that just described The Breport operator notes upon her ticket such report as she has been ableto obtain and places the ticket in the report clip at the right-handsideof the B` dispatch table'. The dispatch operatori at B takes theticket and transmits the report tothe dispatch operator at A over anynon-busy toll line. In transmitting"this' report the B dispatch operatorgives thev A dispatch operator the serialv number and the assignmenttrunk number of thecall which enables'the A operator to readily locatethe ticket relating to this call. The A dispatch operator takes theticket from the assignment clip at `back of her table, leaving thenumber of the assignment trunk to which it hadA been assigned, and:lalf-ter noting. thereon the report received from the B dispatch operatorshe inserts the ticket vertically in the same numbered assignment clip.Since the normal position of tickets placed in the clips upon thedispatch tables is horizont-al, the attention of the report operator atA will be attracted. This operator will then take the ticket, and willring the calling partys telephone by'` operating the key K4. It will beremembered that the report operator at A has previously established acircuit connection'- with the calling party but has not rung over theline. VVh'en` the calling party answers', the report operator `gives herthe report regarding the call, and then files the ticket. The numbercheck which the A report operator hadpreviously inserted in the clip infront of the cord pair associated with this calling partys line isreturned to the assignment clip having the corresponding number.

To enable each of the dispatch operators to determinev quickly7 thestatus of the' as sigm'nent trunks between her dispatch table and thecorresponding report positions, a trunk assignment indicator isprovided. Suchan indicator is show-n in position upon the dispatch tablein Fig. 3' and in detail in Fig.v 3a. rThisy indicator consists of ablock having a sloping face containing, in itssimplestform, three slots.Associated with these slots are.` a number of buttons so arranged as-toslide easily along the said slots and tobe readily removable' therefrom.The upper slot holds only those buttons bearing numbers corresponding tothe' outgoing assignment trunks. In like manner, the middle slot holdsthose buttons corresponding to the` incoming trunks. Since the outgoingtrunksl at oiiice are odd numbered and the incoming trunks even numberedthe corresponding buttons will be soy numbered. The lowest slot isintended to hold the buttons of both types of trunks after the trunkshave been assigned.

The method of using the indicator in order to keep track of the variousassignment trunks is as follows: The buttons corresponding to trunkswhich have not been assigned' to any call are grouped at the right-handend of the yupper and middle slots. After a call has been passed', foreX- ample, from the dispatch yoperator at A to the' dispatch operator atB and an assignment trunk has been assigned to that call, the 'operatorat A wil-l remove the button having the number 0iY the assigned trunkfrom the upper slot and" place it in the lower slot. As soon as a. tollline has been assigned? for the completion' of the call associated withthat particular assignment trunk the button corresponding to this trunkis placed in the upper slot but at the left-hand side thereof. Byglancing at this indicator the dispatch' operator can tell instantly thestatus of. her assignment trunks. Thus, for example, inthe indicatorrepresented by Fig. 3a, trunks 1 and 3 of the outgoing group and trunks2, 4 and 6 ot' the incoming groups are unassigned; trunks 9 andv 1.0"'have been assignedl toparticular calls but no toll line has beenassigned for the completion of the connection: trunks 5 andA 7 of" theoutgoii'ig groups and trunk 8 of the incoming group have been connected'with toll lines. As soon as'any of the calls have been completed overtrunks 5, 7 or 8 the corresponding button will be moved .from theleft-hand toward the right-hand side of the upper or middle slot.

` By means of an indicator performing the functions just described, eachdispatch operator is thereby enabled to quickly determine the status ofany. of her asignment trunks.

During periods of heavytraiiic, calls are passed between dispatchoperators faster than they can be completed. IV. HS. obtained ashereinbefore described accumulate waiting circuits. As each toll line isreleased, it is assignedfto the next IV. H. in order, and for each suchassignment there is, of course, terval as it might be termed, that is,the period from the making of an assignment until both parties concernedare at their telephones ready to talk. During the assignment intervalthe dispatch operators use the toll line to pass new calls, which inturn create new YV. Hs. and to receive reports on calls previouslypassed. In practice it develops that these assignment periods areusually of suiic-ient length to maintain WV. Hs. ahead of the availabletoll lines as long as new business continues to come in heavily. Thefundamental principle upon which the dispatch method of operation isbased is to utilize the assignment periods to the utmost for the purposeof passing a plurality of calls in advance of the time when such callscan be completed, thereby creating a reservoir of parties ready to talkas soon as the toll lines are available. Since in practice it has provedpossible during periods of traflic congestion to keep W. Is. continuallyawaiting assignment, the lost circuit time per message, that is to say,the time not available for conversation, has been approximately reducedto the minimum required to bring to their telephone the persons known tobe available. The application of the aforementioned fundamentalprinciple which underlies the method and means in which this inventionis embodied, results in greatly increasing the circuit efficiency of thedispatch systemof operation by cutting down the amount of lost circuittime (time not available for conversation) which in the ring-down methodof operation and in other known methods of operation heretofore employedwas relatively large and therefore resulted in low operating etliciency.

It has been found in practice that if W. I-I. reports are allowed toaccumulate so that there .is too long' a delay in establishing thecircuit connection one or both of the parties involved will not beavailable after the assignment has been made to a toll line trunk. Toavoid these cancelled as- Consequently one assignment ini`theicharacterdescribed, the method which `signments vwhich reduce theefficiency of the operation, it has been found desirable to pass no newcalls between the dispatch operators after the number of WV. Hs.awaiting assignment to toll lines is equal to twice the number of tollcircuits in the dispatch group, until the numberof W. Hs. has beenreduced to the number of circuits in the group. Y Although, thisinvention has been de scribed as embodied in a certain arrangement-ofmeans, it is to be understood that it is not so limitedbut is capable ofembodiment in otherA and different means without departing from thespirit and scope of the invention as defined in the appended claims.

What is claimed is: l

Ll. In a despatch toll telephone system of consists in transmitting overany non-busy toll line from the outward to the inward despatch operatorthe details of a toll telephone call, obtaining a report regarding thecalled party, holding the called partys line if that party accepts thecall, transmitting over any non-busy toll line from the inward to theoutward despatch operator a report concerning the said call, assigning atoll line for ultimate use in establishing a circuit for the said call,building up proper terminal arrangements for completion of the saidcall, and maintaining the terminal circuits effectively disconnectedfrom the said toll line until the calling and the called parties areready to talk, whereby the said toll line is available to the despatchoperators for the transmittal of further calls, reports, etc., aftersuch assignment has been made and substantially up to the time when theparties begin talking.

2. In a despatch toll telephone system of the character described, themethod which consists in recording the details of a toll telephone call,transmitting such record over any non-busy toll line to the despatchoperator at the called ofiice, assigning a serial number to such calland also assigning the said call to an idle assignment trunk, taking upwithout ringing the calling subscribers line, establishing a connectionwith the called party and holding the said partys line, transmitting a`report from the called toll otlice'tothe calling toll office over anynon-busy toll line that the called-.party is available, assigning thesaid call to any nonbusy toll line, ringing the calling and the calledparties from their respective despatch tables, supervising the saidcalls by the re spective report operators, signaling the respectivedespatch operators `that `the parties are ready, transmitting a readywith7 sig- .nal by the despatch operator who first receives a signalfrom her report operator that her party is ready, transmitting a goahead signal by that despatch operator who last receives such a signal,and' then effectively connecting, both parties with the toll line.

3. In a despatch toll telephone system characterized by two tollboards,connected by a plurality of toll? lines, eachf board having a despatchtable and a report position thereat, assignment trunks connecting saidtable and said position, switching trunks extending. fromV said: boardsto locall central oflices, cord circuits to connect thev said switching'trunks with the said assignment trunks and cord circuits to connect thesaid assignment trunks with the said toll lines, the method of operatingthe said system which consists in transmitting over any non-busy tollline a call from the outward despatch operator tothe inward despatchoperator and releasing,` the said line, getting a, report upon the saidlcall by' they inward report operator, transmitting over any nonhusy tolllinea report upon the said call by the inward despatch operator to theoutward despatch operator and releasing the' said tolly line, andcalling. the respective parties to Vtheir telephonesbut maintaining saidterminal circuits effectively disconnected from the assigned toll lineuntil both arties are at their telephones and are ready.'

In testimony whereof, I have signed myf name to thisl specification this22nd day of June; 1923;

ERNEST A. GRAY.

